HPAChildren treated with the Pandemrix flu vaccination could be at risk of developing narcolepsy, scientists from the Health Protection Agency (HPA) have warned.

The Pandemrix vaccine was mainly prescribed to treat serious complications during the pandemic flu outbreak in 2009/10, and was used intermittently to treat children in the 2010/11 flu season.

Yet the study, by the HPA and researchers from Papworth and Addenbrooke hospitals in Cambridge, looked at 75 cases of children (aged 4-18 years of age) diagnosed with narcolepsy from January 2008.  They found that 11 of the children had been vaccinated before their symptoms began, with 7 cases occurring within 6 months.

This suggests a risk of narcolepsy following vaccination with Pandemrix of 1 in every 55,000 doses. The report also backs up findings by scientists in Finland and Sweden.

Lead author Professor Liz Miller, a consultant epidemiologist with the HPA, said: “These findings suggest there is an increased risk in children of narcolepsy after Pandemrix vaccination and this is consistent with findings from studies in other European countries. However, this risk may be overestimated by more rapid referral of vaccinated cases. Long term follow up of people exposed to Pandemrix is needed before we can fully establish the extent of the association.

“Our findings have implications for the future licensing and use of adjuvanted pandemic vaccines. Further studies to assess the possible risk associated with other vaccines used in the pandemic, including those with and without adjuvants, are also needed to inform the use of such vaccines in the event of a future pandemic.”

Narcolepsy is a chronic neurological disorder caused by the brain’s inability to control sleep. It leads to excessive daytime sleepiness accompanied by sudden episodes of muscle weakness. Around 20,000 people in the UK are affected by narcolepsy, although most manage the condition with drug treatment and lifestyle measures.

The findings were published in the British Medical Journal.